Indoor suspended lighting fixtures such as those used in warehouse and other commercial and retail settings typically utilize high intensity discharge (HID) lamps because of their superior efficiency and high light output. As those skilled in the art will recognize, however, these lamps and other high wattage light sources have been found to be susceptible to non-passive end of life failure particularly when operated continuously for all or a substantial part of their useful life.
Non-passive lamp failures generally occur in response to crack propagation of the associated arc tube. Specifically, when the internal arc tube ages and develops minute faults, the lamp may crack thus allowing the high pressure to force hot arc tube fragments through the outer glass jacket. If the associated luminaire is not suitably enclosed, falling arc tube fragments may, of course, pose a danger to personnel and property. Because many luminaires are not enclosed, non-passive end of life light source failure continues to be an issue of great concern to lamp manufacturers and lighting designers.
To prevent non-passive light source failures, high intensity discharge lamp manufacturers recommend periodic cycling of all lamps. Where lamps are used in applications that run continuously, lamp manufacturers require regular cycling typically once a week.
In operation, the high wattage light source such as, for example, an HID lamp, is periodically cycled off and then back on. An arc tube that has developed a weakness will fail during the cool down and subsequent warm up cycle because of the additional thermal contraction and expansion stresses experienced by the arc tube. To accomplish the required cycling of these lamps, the owner of the facility must de-energize then re-energize an entire electrical circuit. Because in many applications the lamps are running continuously, however, such cycling interrupts the facility's operation. Unless timers are attached to each circuit, there is also the possibility that an owner or her representative will not perform this cycling on a regular basis.
Consequently, a need exists for an improved electrical assembly for a luminaire which is adapted to automatically turn off a light source so as to promote passive end of life light source failure and substantially reduce or eliminate danger to personnel and property especially in open luminaire applications.